Magnetism of PrFeAsO parent compound for iron-based superconductors: M\"ossbauer spectroscopy study

TL;DR

This study uses Mössbauer spectroscopy to analyze the magnetic ordering and structural changes in PrFeAsO, revealing the development of SDW, praseodymium magnetic order effects, and nematic phase characteristics in this parent compound of iron-based superconductors.

Contribution

It provides detailed insights into the magnetic and structural evolution of PrFeAsO, highlighting the interplay between SDW, praseodymium order, and nematic phases using Mössbauer spectroscopy.

Findings

It develops an itinerant 3d magnetic order at ~165 K.

A complete incommensurate SDW forms at ~140 K.

Praseodymium magnetic order influences SDW enhancement.

Abstract

Moessbauer spectroscopy measurements were performed for the temperature range between 4.2 K and 300 K in a transmission geometry applying 14.41-keV resonant line in 57Fe for PrFeAsO the latter being a parent compound of the iron-based superconductors belonging to the '1111' family. It was found that an itinerant 3d magnetic order develops at about 165 K and it is accompanied by an orthorhombic distortion of the chemical unit cell. A complete longitudinal 3d incommensurate spin density wave (SDW) order develops at about 140 K. Transferred hyperfine magnetic field generated by the praseodymium magnetic order on iron nuclei is seen at 12.8 K and below, i.e., below magnetic order of praseodymium magnetic moments. It is oriented perpendicular to the field of SDW on iron nuclei. The shape of SDW is almost rectangular at low temperatures and it transforms into roughly triangular form around 'nematic' transition at about 140 K. Praseodymium magnetic order leads to the substantial enhancement of SDW due to the large orbital contribution to the magnetic moment of praseodymium. A transferred field indicates presence of strong magnetic susceptibility anisotropy in the [b-c] plane while following rotation of praseodymium magnetic moments in this plane with lowering temperature. It was found that 'nematic' phase region is a region of incoherent spin density wavelets typical for a critical region.